Backlight module

ABSTRACT

A backlight module comprises at least a light-guide plate, a palette device and an LED bar. The palette device comprises a palette and light-guide bar and at least one palette LED. The palette and light-guide bar is disposed at a side end of the light-guide plate and has a light-input surface, a light-output surface corresponding to the light-input surface, a first side, a second side corresponding to the first side, a top, and a bottom corresponding to the top. The palette LED is adjacent to the first side and provides a palette light into the palette and light-guide bar. The LED bar is adjacent to the light-input surface of the palette and light-guide bar. The LED bar emits an incident light, which is through the light-input surface into the palette and light-guide bar, wherein a light mixed by the incident light and the palette light is output through the light-output surface is and the side end into the light-guide plate so as to be a light source of the backlight module.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a backlight module, moreparticularly to a backlight module having a palette device.

2. Description of the Prior Art

A general display with the feature of autoluminescence as an LCD mayneed a backlight source for displaying images. For several priorbacklight technologies, the backlight module with the feature ofinputting light from a side end thereof may be more demanded to theneeds of slim product. Such technologies are being widely applied to thescreen of a laptop computer and an LCD.

With references to FIG. 1 and FIG. 2, which illustrates a schematic viewof a prior backlight module and a schematic view of a light-guide plateand an LED bar of the prior backlight module. As shown in the figures, abacklight module 10 includes a light-guide plate 11, an LED bar 12, areflector 13, and a plurality of optical films 14. The light-guide plate11 has a side end 111 and an emergent surface 112. The LED bar 12 isdisposed at the side end 111 of the light-guide plate 11. The pluralityof optical films 14 are disposed on the emergent surface 112 of thelight-guide plate 11. The reflector 13 is disposed on the bottom of thelight-guide plate 11, wherein the bottom is corresponding to theemergent surface 112.

A plurality of white light LEDs 121 are disposed at the LED bar 12 andcorresponding to the side end 111 of the light-guide plate 11 in orderto emit a linear light. The linear light from the LED bar 12 passesthrough the side end 111 of the light-guide plate 11 and then into thelight-guide plate 11. The incident linear light from the LED bar 12 istotally reflected within the light-guide plate 11 due to a totalreflection interface in the light-guide plate 11. Continuously, thelight is output from the emergent surface 112 and passes through theplurality of optical films 14 to an LCD not shown in the figures.

The area of the emergent surface 112 is almost the same as the display,that is, the backlight module 10 is able to provide a uniform area lightto the display.

Further, the plurality of optical films 14 have at least one brightnessenhancement film and at least one diffuser in order to strengthen thelight quality provided by the backlight module. The reflector 13 belowthe light-guide plate 11 is to avoid the incident light emittingdownwardly and promote the usage rate of light.

As aforesaid, the LED bar 12 emits white light by means of the whiteLEDs 121. Generally speaking, the white LED 121 emits a white light byway of a blue LED motivating yellow florescence, that is, a florescentwhite light LED. The color of the white light LED is closer to the bluecolor tone and short of red color tone. Thus, the color of the LCD is alittle bit ashy.

Other factors as the changeable wavelengths of the blue light LED, thechangeable contents of the florescence and the differences between thethicknesses of the light-guide plates are the key roles to cause thewhite light closer to the blue color tone. In another word, thedifferences between different color tones make error distributions incolor coordinates (x, y). Hence, QC is hardly made.

A distribution range of the white light LED in color coordinates (x, y)is around 0.28 to 0.32. If under the condition of 6500K (D65) of a colortemperature, the color coordinates is (0.31, 0.32). The variety (Δx, Δy)must be controlled within 0.005 so as to control the color coordinatesin a better range.

Presently the distribution range is very broad, and applicative LEDsmust be filtered by way of color bin sorting. The only consideration isthat the sorted categories may be hundreds so as to cause the problemsof overstock, oversorting and labor cost. Besides, the color coordinatesof some light from some LEDs are too small so as to cause a condition ofhard usage and that the color tone is closer to ashy, and then a defectrate is highly increased.

As a conclusion, how to make the color tone of a backlight module agreewith the needs of a display in order to represent the true colors ofimages will be the first priority to the persons skilled in the art.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a backlightmodule with a palette device. By means of the palette device, the lightsource of the backlight module can be adjusted in order to produce thelight with uniform color tone.

The backlight module at least comprises a light-guide plate, a palettedevice and an LED bar.

The light-guide plate has a side end, which is a light incident end. Thepalette device has a palette and light-guide bar and at least onepalette LED. The palette and light-guide bar is a hexahedral member andhas a light-input surface, a light-output surface corresponding to thelight-input surface, a first side, a second side corresponding to thefirst side, a top, and a bottom corresponding to the top. The paletteand light-guide bar is disposed at the outside of the side end of thelight-guide plate, and the light-output surface is connected to the sideend of the light-guide plate.

The palette LED is adjacent to the first side and providing a palettelight, which passes through the first side into the palette andlight-guide bar.

It is to be noted that the light-output surface of the palette andlight-guide bar has a plurality of micro scatter structures, and thepalette light from the palette LED passes through the micro scatterstructures so as to form a uniform linear light source.

The LED bar is adjacent to the light-input surface of the palette andlight-guide bar and has a plurality of LEDs. The LED bar emits anincident light, which is through the light-input surface into thepalette and light-guide bar, wherein a light mixed by the incident lightand the palette light is output through the light-output surface and theside end into the light-guide plate.

Preferably, the LED bar is a white light LED bar. The palette LED canonly be disposed adjacent to the first side, or both ends of the paletteand light-guide bar, that is, around the first side and the second side.Further, the number of the LEDs is demanded by different color tones.

Other and further features, advantages, and benefits of the inventionwill become apparent in the following description taken in conjunctionwith the following drawings. It is to be understood that the foregoinggeneral description and following detailed description are exemplary andexplanatory but are not to be restrictive of the invention. Theaccompanying drawings are incorporated in and constitute a part of thisapplication and, together with the description, serve to explain theprinciples of the invention in general terms. Like numerals refer tolike parts throughout the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, spirits, and advantages of the preferred embodiments of thepresent invention will be readily understood by the accompanyingdrawings and detailed descriptions, wherein:

FIG. 1 illustrates a schematic view of a prior backlight module;

FIG. 2 illustrates a schematic view of a light-guide plate and an LEDbar of the prior backlight module;

FIG. 3A illustrates a schematic view of a backlight module of thepresent invention;

FIG. 3B illustrates a schematic view of a palette device of thebacklight module of the present invention;

FIG. 4 illustrates a front view of the palette device of the presentinvention;

FIG. 5 illustrates a schematic view of the light illumination of apalette and light-guide bar of the palette device of the presentinvention;

FIG. 6A illustrates a schematic view of only one end providing a palettelight of the first preferred embodiment of the present invention;

FIG. 6B illustrates a schematic view of the light illumination of onlyone light entering into the one end of the palette and light-guide barof the present invention;

FIG. 7A illustrates a schematic view of two ends providing two palettelights of the second preferred embodiment of the present invention;

FIG. 7B illustrates a schematic view of the light illumination of twolights entering into the two ends of the palette and light-guide bar ofthe present invention;

FIG. 8A illustrates a schematic view of only one end providing a palettelight of the third preferred embodiment of the present invention; and

FIG. 8B illustrates a schematic view of two ends providing two palettelights of the fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With references to FIG. 3A and FIG. 3B, which illustrate a schematicview of the backlight module of the present invention and a schematicview of a palette device of the backlight module of the presentinvention.

As shown in the figures, the backlight module adopts a side end thereofto be a role for inputting light. The backlight module includes alight-guide plate 21, a palette device 25 and an LED bar 22.

The light-guide plate 21 has a side end 211, which is a light incidentend. The palette device 25 has a palette and light-guide bar 23 and apalette LED 241.

The palette and light-guide bar 23 is at least a hexahedral member, butcan be a heptahedron, an octahedron or a polyhedron with more than eightsurfaces as well. Preferably, the palette and light-guide bar 23 is ahexahedral member and has a light-input surface 233, a light-outputsurface 234 corresponding to the light-input surface 233, a first side231, a second side 232 corresponding to the first side 231, a top 235,and a bottom 236 corresponding to the top 235. The palette andlight-guide bar 23 is disposed at the outside of the side end 211 of thelight-guide plate 21, and the light-output surface 234 is connected tothe side end 211 of the light-guide plate 21.

Preferably, the palette and light-guide bar 23 is made of transparentplastic material, such as PC or PMMA. The first side 231, the secondside 232, the top 235, the bottom 236, and the light-input surface 233are all slickensides.

The first palette LED 241 is adjacent to the first side 231 and providesa palette light, which passes through the first side 231 into thepalette and light-guide bar 23.

Preferably, the palette device 25 further includes a second palette LED242 adjacent to the second side 232, the second palette LED 242 providesa palette light which passes through the second side 232 into thepalette and light-guide bar 23.

In other words, the palette LED can only be disposed adjacent to thefirst side 231, or both ends of the palette and light-guide bar 23, thatis, around the first side 231 and the second side 232. Further, forother preferred embodiments, the number of the first palette LEDs 241 orthe second palette LEDs 242 is demanded by different color tones.

Besides, the first palette LEDs 241 or the second palette LEDs 242 maycomprises red light LEDs, green light LEDs, blue light LEDs, all-in-oneLEDs, or multi-assembly LEDs.

Please refer to FIG. 3A and FIG. 3B again, the light-output surface 234of the palette and light-guide bar 23 has a plurality of micro scatterstructures 238, and the palette light from the first palette LED 241 orthe second palette LED 242 passes through the micro scatter structures238 so as to form a uniform linear light source. Preferably, the microscatter structure 238 can be a protrusion structure, which ishemisphere, cone, cuboid, or other micro structures; on the other hand,the micro scatter structure 238 can be a concave structure, which ishemisphere, cone, cuboid, or other micro structures.

The LED bar 22 is adjacent to the light-input surface 233 of the paletteand light-guide bar 23 and has a plurality of LEDs 221. The LED bar 22emits an incident light, which is through the light-input surface 233into the palette and light-guide bar 23, and the incident light is thenoutput from the light-output surface 234. Wherein a light mixed by theincident light from the LED bar 22 and the palette light from the firstpalette LEDs 241 or the second palette LEDs 242 is output through theside end 211 into the light-guide plate 21.

For the preferred embodiment, the LED bar 22 has the plurality of whitelight LEDs 221, and the light from the light-guide plate 21 is mixed bythe white light LEDs 221, the first palette LEDs 241 and the secondpalette LEDs 242. So the color tone of the mixed light may not be closerto the color tone of ashy, and represent proper color tone.

Preferably, for more effective usage to the light in the palette andlight-guide bar 23, the top 235 and the bottom 236 may have a totalreflection layer respectively in order to avoid the leakage of light.The light-output surface 234 of the palette and light-guide plate 23 isconnected to the side end 211 of the light-guide plate 21 so as toeffectively transmit the light in the palette and light-guide plate 23into the light-guide plate 21 by means of the light-output surface 234.

Preferably, for the dimensions of the palette and light-guide bar 23,the distance between the first side 231 and the second side 232, that isthe length L of the palette and light-guide bar 23, is equal to thelength of the light-guide plate 21 practically. The distance between thetop 235 and the bottom 236, that is, the thickness H of the palette andlight-guide bar 23, is equal to the thickness of the light-guide plate21 practically. So that the incident light from the LED bar 22 and thepalette lights from the palette LEDs 241 and 242 are effectivelytransmitted into the light-guide plate 21. The distance between thelight-input surface 233 and the light-output surface 234, that is, thewidth w of the palette and light-guide bar 23, is determined upon thepalette demands including the dimensions and the numbers of LED.

With reference to FIG. 4, which illustrates a front view of the palettedevice 25 of the present invention. The palette lights from the firstpalette LED 241 and the second palette LED 242 are transmitted into thepalette and light-guide bar 23 via the first side 231 and the secondside 232 respectively, continuously the lights are output through themicro scatter structures 238. For a uniform linear light source producedby the palette and light-guide bar 23, the dimensions and the pitches ofthe micro scatter structures are the most important factors while indesign.

With reference to FIG. 3B and FIG. 4, the light illumination of thefirst palette LED 241 is assumed as I0, the area of the first side 231is A0. The micro scatter structure 238 is a concavity structure with theshape of hemisphere and has a diameter d. The pitch of two micro scatterstructures is p. The light illumination of a light emitted from alocation x is

${\frac{\mathbb{d}{I(x)}}{\mathbb{d}x} = {\alpha\;{I(x)}}},$wherein α is a scatter coefficient, which is related to the diameter dand pitch p of the micro scatter structures and described as thefollowing equation:α≅d²/A₀*p   (1),since dI(x)=−αI(x)dx   (2),then I(x)=I ₀ e ^(−αx)   (3).

From equation (3), assuming that the scatter coefficient α is aconstant, the light illumination is inversely proportional to x. Forinstance, assuming that L=300 mm, H=1 mm, W=5 mm, p=1 mm, and α=1/150,then I(x=L)/I₀=e^(−(300/150))=0.13. In another word, the light from thefirst palette LED 241 is transmitted from the location of x=0 mm tox=300 mm, the residue of the light is only 13.5%. Which means the lightillumination is decreased by the increase of x.

On the other hand, equation (4) as:α=d ² /A ₀ ·p=α=d ² /W·H·p=1/150 ,the diameter d≅0.18 mm.Equation (5) as d²/H·p=the area of the micro scatter structures 238/thearea of the light-output surface 234 shall determine a ration of5/150=1/30 . That is, while the light from the LED bar 22 passingthrough the light-input surface 233 is being output through thelight-output surface 234, 3.3% of the light will be refracted by themicro scatter structures 238. And a half of 3.3% (around 1.6%) will beagain refracted to the light-input surface 233 and the LED bar 22 so asto cause some loss, which is very tiny and can be ignored.

From equation (3), the palette light is scattered through thelight-output surface 234 is an exponentional decrease.

As shown in FIG. 4, if α=1/150, and the first palette LED 241 and thesecond LED 242, which have the same illumination, are disposed at thefirst side 231 and the second side 232 respectively, the combined lightillumination is represented as I_(T)(x)=I₁(x)+I₂(x) and can be seen inFIG. 5. Due to I₁(x=L/2)/I₀=0.37 and I₁(x=L)/I₀=I₂(0)=0.13, the combinedlight illumination is as:I _(T)(0)=I ₁(0)+I ₂(0)=1.13, and I _(T)(L/2)=I ₁(L/2)+I ₂(L/2)=0.74.

Due to aforesaid equations and FIG. 5, the light illumination at L/2,which is the middle of the palette and light-guide bar 23, is 65% of thelight illumination of the two ends, therefore the output light is notuniform.

To improve the problem of uneven scattered light can depend on thedevelopment of equation (2). To make a uniform scattered palette light,dI(x)/dx must be a constant in equation of dI(x)/dx=−αI(x). That is,dI(x)/dx=−αI(x)=−CI ₀   (6),wherein constant C is an expected scatter rate. From equation (6), twofollowing equations as below:I(x)=I ₀(1−Cx)   (7)α(x)=C/(1−Cx)   (8)As shown in equation (8), the scatter coefficient α(x) is not a constantand increased with x.

As an example, if L=300 mm, H=1 mm, W=5 mm, and p=1 mm, only the firstpalette LED 241 is disposed around the first side 231, that is, only onepalette light at one end is provided to pass through the first side 231and into the palette and light-guide bar 23, and I(x=L)=0.13I₀, whichmeans 13% of palette light are not scattered. Therefore, C=0.0029 mm⁻¹from equation (7), and from equation (8), an equation is gained as:α(x)=0.0029/(1−00029x)   (9),and substituted in equation (1), then it is shown as:α≅d²/A₀·p=0.0029/(1−0.0029x), so the variation of the diameter of themicro scatter structure 238 is represented as:d(x)=[0.0029/(1−0.0029x)·5×1]^(1/2) mm   (10),while x=0, d(0)=0.12 mm; x=L/2, d(L/2)=0.16 mm; and x=L, d(L)=0.33 mm.

With references to aforesaid, only the first palette LED 241 is disposedaround the first side 231 and only one palette light at one end isprovided to pass through the first side 231 and into the palette andlight-guide bar 23, the diameter/dimensions of the micro scatterstructures 238 are variable based on equation (10) so as to have auniform output light source.

Referring to FIG. 6A, which illustrates a schematic view of only one endproviding a palette light of the first preferred embodiment of thepresent invention. As shown in the figure, only the first palette LED241 is disposed around the first side 231, and therefore only onepalette light at one end is provided to pass through the first side 231and into the palette and light-guide bar 23. Continuously the palettelight is scattered through the micro scatter structures 238 of thelight-output surface 234. Wherein the diameter/dimensions of the microscatter structures 238 are being larger while such micro scatterstructures 238 are farther from the first side 231. For the preferredembodiment, the second side 232 of the palette and light-guide bar 23can be a total reflection layer 28 so as to completely use the palettelight. In other words, every palette light can be output via the microscatter structure 238.

With reference to FIG. 6B, which illustrates a schematic view of thelight illumination of only one light entering into the one end of thepalette and light-guide bar of the present invention. The lightillumination I(x) is decreased with the increase of x. But for thepreferred embodiment, the scatter coefficient α(x) is not constant, andit is increased with the increase of x. That is, the dimensions of themicro scatter structure 238 are increased with the increase of x.Therefore, the light illumination of the palette light,dI(x)/dx∝α(x)I(x), may not be increased with the increase of x. Hence,the palette and light-guide bar 23 of the preferred embodiment canproduce a uniform linear light source.

For the second preferred embodiment, if L=300 mm, H=1 mm, W=5 mm, andp=1 mm, the first palette LED 241 and the second palette LED 242 aredisposed around the first side 231 and the second side 232 respectively,and the palette lights from the outside of the two ends pass through thefirst side 231 and the second side 232 and then into the palette andlight-guide bar 23. Meanwhile, the scattered light output from thepalette and light-guide bar 23 is the combination of the lightillumination I₁ and light illumination I₂. Wherein the lightilluminations of the first palette LED 241 and the second palette LED242 are assumed to be the same as the color tone.

The difference between the first preferred embodiment and the secondpreferred embodiment is that of the second preferred embodiment adoptingtwo palette lights provided from the outside of the two ends of thepalette and light-guide bar 23. So that, d must be varied with thelocation at L/2 of the palette and light-guide bar 23 symmetrically.That is, for equation (10), the scope of variation of x is from 0 toL/2; especially, the structure must be designed symmetrically whilex≧L/2.

With reference to FIG. 7A, which illustrates a schematic view of twoends providing two palette lights of the second preferred embodiment ofthe present invention. As shown in the figure, the first palette LED 241and the second palette LED 242 are disposed around the first side 231and the second side 232 respectively, and the lights from the outside ofthe two ends pass through the first side 231 and the second side 232 andthen into the palette and light-guide bar 23. Then the palette lightsare scattered through the micro scatter structures 238 of thelight-input surface 234. Wherein the dimensions/diameters d of the microscatter structures 238 are being symmetrically increased from both thefirst side 231 and the second side 232 to the middle, where is L/2.

With reference to FIG. 7B, which illustrates a schematic view of thelight illumination of two lights entering into the two ends of thepalette and light-guide bar of the present invention. As shown in thefigure, the combined illumination of the whole scattered light isrepresented as dI₁(x)/dx+dI₂(x)/dx. As it can be seen, the 5 combinedillumination may not be changed with x almost. Hence, the palette andlight-guide bar 23 can definitely produce a uniform linear light source.

With the comparison of FIG. 6A and FIG. 7A, the area ratio of the microscatter structures 238 and the light-output surface 234 of FIG. 6A islarger than the area ratio of the micro scatter structures 238 and thelight-output surface 234 of FIG. 7A. Hence, the incident light of theLED bar 22 in the preferred embodiment of FIG. 7A is lost less than thepreferred embodiment of FIG. 6A.

There is another way to make the scattered light be uniform, that is, toadjust the pitch p among the micro scatter structures 238. From equation(11) as α(x)=d²/A₀·p=C/(1−Cx), another equation (12) asp=(d²/A·C)·(1−Cx) is gained. For instance, if L=300 mm, H=1 mm, W=5 mm,d=0.12 mm, and C=0.0029, and only the first palette LED 241 is disposedaround the first side 231, hence only one light goes through the firstside 231 and enters into the palette and light-guide bar 23. Fromequation (12), the first result is that p=1.0 mm while x=0; the secondresult is that p=0.56 mm while x=L/2.

With references to aforesaid, only the first palette LED 241 is disposedaround the first side 231 and only one palette light at one end isprovided to pass through the first side 231 and into the palette andlight-guide bar 23, the pitches of the micro scatter structures 238 arevariable based on equation (12) so as to have a uniform output lightsource.

Referring to FIG. 8A, which illustrates a schematic view of 5 only oneend providing a palette light of the third preferred embodiment of thepresent invention. As shown in the figure, only the first palette LED241 is disposed around the first side 231, and therefore only onepalette light at one end is provided to pass through the first side 231and into the palette and light-guide bar 23. 1o Continuously the palettelight is scattered through the micro scatter structures 238 of thelight-output surface 234. Wherein the pitches of the micro scatterstructures 238 are being smaller while such micro scatter structures 238are farther from the first side 231. In another word, the micro scatterstructures 238 are closer while the is micro scatter structures 238 isbeing close to the second side 232, that is, x=L. Thus, the thirdpreferred embodiment does produce a uniform linear light source.

For the preferred embodiment, the second side 232 of the palette andlight-guide bar 23 can be a total reflection layer 28 20 so as tocompletely use the palette light. In other words, every palette lightcan be output via the micro scatter structure 238.

For the fourth preferred embodiment, the first palette LED 241 and thesecond palette LED 242 are disposed around the first side 231 and thesecond side 232 respectively, and the palette 25 lights from the outsideof the two ends pass through the first side 231 and the second side 232and then into the palette and light-guide bar 23. P must be varied withthe location at L/2 of the palette and light-guide bar 23 symmetrically.That is, for equation (12), the scope of variation of x is from 0 toL/2; especially, the structure must be designed symmetrically whilex≧L/2. the combined illumination of the whole scattered light isrepresented as dI₁(x)/dx+dI₂(x)/dx. As it can be seen, the combinedillumination may not be changed with x almost. Hence, the palette andlight-guide bar 23 can definitely produce a uniform linear light source.

With reference to FIG. 8B, which illustrates a schematic view of twoends providing two palette lights of the fourth preferred embodiment ofthe present invention. As shown in the figure, the first palette LED 241and the second palette LED 242 are disposed around the first side 231and the second side 232 respectively, and the lights from the outside ofthe two ends pass through the first side 231 and the second side 232 andthen into the palette and light-guide bar 23. Then the palette lightsare scattered through the micro scatter structures 238 of thelight-input surface 234. Wherein the pitches d of the micro scatterstructures 238 are being symmetrically decreased from both the firstside 231 and the second side 232 to the middle, where is L/2. In anotherword, the micro scatter structures 238 are closer while the microscatter structures 238 is being close to the middle, that is, x=L/2.Thus, the fourth preferred embodiment does produce a uniform linearlight source.

For the backlight module of the present invention, the backlight sourceis formed as that of the mixed light by the incident light from the LEDbar 22 and the light from the first palette LED 241 or the secondpalette LED 242 passing through the side end 211 of the light-guideplate 21 and then entering into the light-guide plate 21. It is to benoted, the luminous flux may not be too much during the palette process,even only one or several LEDs will be enough.

Taking a 12-inch backlight module as an example, the white light LED barhas 60 LEDs. The luminous flux of each white light LED is 5 lumens, andthe average coordinates are (0.3, 0.3). If using a set of red lightLEDs, which luminous flux is 20 lumens and coordinates are (0.7, 0.7),the estimation is as follows:x=X/(X+Y+Z),y=Y/(X+Y+Z)   (13),wherein x, y and z are tri-stimulus values from CIE1931. Thus, the totalstimulus value of the whole white light LED bar is:X+Y+Z=Y/y=60×5/0.3=1000 lumens.If adding more red light LEDs, the values of Δx and Δy. And

X=x/y(

Y), thus

X=0.7/0.3×20=46 if

Y of the added red light LEDs is 20 lumens.

The coordinates can be determined by equation (13), and they are shownas:

x≅

X/(X+Y+Z)=46/1000=0.046, and

y≅

Y/(X+Y+Z)=20/1000=0.02.Thus, the color coordinates of the backlight module are (0.346, 0.32)after the palette process.

According to above analysis, only adding a set of red light LEDs with 20lumens, the color coordinates (

x,

y) can be adjusted to (+0.046, +0.02). Further, adding a set of redlight LEDs with 40 lumens, the color coordinates (

x,

y) can be adjusted to (+0.012, +0.04).

Nowadays, high-illumination LEDs are popular already. For the field ofhigh efficiency, the red light LED can reach 100 lumens/watt, and thegreen light LED can reach above 120 lumens/watt. The luminous flux of alow power red light LED approaches 5 lumens, and the luminous flux of alow power red light LED approaches beyond 8 lumens.

Thus, only four low power red light LEDs can reach the palette scope ofΔx≈0.034, and five low power red light LEDs can reach the palette scopeof Δy≈0.04.

According to above analysis, adding red light LED may add X stimulusvalue of the tri-stimulus values. The wavelength of red light LED justmatches with the high receiving wavelength of the red filter of thecolor filters of LCD, therefore the added red light can be almost outputby the color filters.

Due to that the most wavelength of white light is absorbed while in theprocess of wavelength allocation and in the receiving area of the redcolor of the color filters, the tone of output white light is closer toashy so as to represent the color tone of skin abnormally. Hence, addingsome red light may highly improve the color tone of skin.

If using the palette device to adjust the color coordinates of thebacklight module, the adjustment can be done from Δ x or

y to positive or from

x or

y to negative. As aforesaid, adding red light LED may adjust

x toward positive; adding green light LED may adjust

y toward positive as well. On the other hand, to adjust the colorcoordinates toward negative, adding blue light LED is a must.

Generally speaking, the color coordinates of blue light LED are (0.15,0.05). If the total luminous flux is 8 lumens, then

Z=(1−x−y)/y×

Y, wherein

Y is equal to the total luminous flux, which is 8 lumens. Then

Z=(1−0.15−0.05)/0.05×8=128 lumens.

Since

X and

Y of the tri-stimulus values of blue light LED are tiny, thus only

Z should be considered. Continuously, the color coordinates of addingblue light LED can be gained by below equation:

$\begin{matrix}{x^{1} = \frac{X}{X + Y + Z + {\Delta\; Z}}} \\{= {\frac{X}{X + Y + Z} \cdot \frac{1}{\left( {1 + \frac{\Delta\; Z}{X + Y + Z}} \right)}}} \\{{\cong {x\left( {1 - \frac{\Delta\; Z}{X + Y + Z}} \right)}},}\end{matrix}$Hence, the variation of the color coordinates of x is as:

${\Delta\; x} = {{x^{1} - x} = {{- x} \cdot \frac{\Delta\; Z}{X + Y + Z}}}$${\Delta\; y} = {{- y} \cdot \frac{\Delta\; Z}{X + Y + Z}}$Then,Δx=−0.15×(128/1000)=−0.02, andΔy=−0.05×(128/1000)=−0.004. The purpose of lowering the colorcoordinates is approached. Consequently, adding some palette LEDs, whichis red, green or blue, to the first side 231 and the second side 232 atthe two ends of the palette and light-guide bar 23 and the white lightLED bar 22 being disposed at the light-input surface 233 of the paletteand light-guide bar 23, aforesaid purpose is approached.

The incident light of the white light LED bar 22 is input from thelight-input surface 233 and output from the light-output surface 234.The palette light from the palette LEDs is input from the first sideand/or the second side and output from the micro scatter structure 238.Meanwhile, the output light from the light-input surface 233 of thepalette and light-guide bar 23 is mixed by the incident light and thepalette light and shaped as a uniform linear light source, which isoffered to the light-guide plate 21 of the backlight module.

In practice, by means of some light-test and color-test devices tomeasure and adjust the pulse width of the PWM (pulse width modulation)for precisely controlling the light illumination, the actual colorcoordinates can then be reached. Further, the demand of highlyuniformity within 0.005 of (

x,

y) is gained.

As a conclusion, the advantages of the present invention are listedbelow.

-   1. By means of the palette device, the backlight source of the    backlight module is adjustable in order to produce uniform color    tone.-   2. The light source provided by the backlight module of the present    invention can be in the process of palette. So that the color tone    of LCD may not be closer to ashy color and be represented properly.-   3. The palette LED/LEDs of the palette device are disposed at the    one end or two ends of the palette and light-guide bar; further, the    dimensions, positions or distribution density of the micro scatter    structures of the light-output surface are adjustable. Thus, both    features make a uniform linear light source.

Although this invention has been disclosed and illustrated withreference to particular embodiments, the principles involved aresusceptible for use in numerous other embodiments that will be apparentto persons skilled in the art. This invention is, therefore, to belimited only as indicated by the scope of the appended claims.

1. A backlight module comprising: a light-guide plate having a side end; a palette device comprising: a palette and light-guide bar, which is at least a hexahedral member and has a light-input surface, a light-output surface corresponding to the light-input surface, a first side, a second side corresponding to the first side, a top, and a bottom corresponding to the top, the palette and light-guide bar being disposed at the outside of the side end of the light-guide plate, and the light-output surface being connected to the side end of the light-guide plate, wherein the light-output surface has a plurality of micro scatter structures; and at least one first palette LED being adjacent to the first side and providing a palette light, which passes through the first side into the palette and light-guide bar; and an LED bar being adjacent to the light-input surface of the palette and light-guide bar and having a plurality of LEDs, the LED bar emitting an incident light, which is through the light-input surface into the palette and light-guide bar, wherein a light mixed by the incident light and the palette light is output through the light-output surface and the side end into the light-guide plate.
 2. The backlight module according to claim 1, wherein the micro scatter structure is selected from the protrusion structure group of hemisphere, cone and cuboid.
 3. The backlight module according to claim 1, wherein the micro scatter structure is selected from the concave structure group of hemisphere, cone and cuboid.
 4. The backlight module according to claim 1, wherein the dimensions of the micro scatter structures are gradually larger while the distance between the micro scatter structures and the first side is gradually larger.
 5. The backlight module according to claim 1, wherein the palette device further comprises a second palette LED adjacent to the second side, the second palette LED provides a palette light which passes through the second side into the palette and light-guide bar, the dimensions of the micro scatter structures are being larger from the first side and the second side of the two ends of the palette and light-guide bar to the middle portion thereof.
 6. The backlight module according to claim 1, wherein each pitch of the micro scatter structures is gradually smaller while the distance between the micro scatter structures and the first side is gradually larger.
 7. The backlight module according to claim 1, wherein the palette device further comprises a second palette LED adjacent to the second side, the second palette LED provides a palette light which passes through the second side into the palette and light-guide bar, the pitches of the micro scatter structures are being smaller from the first side and the second side of the two ends of the palette and light-guide bar to the middle portion thereof.
 8. The backlight module according to claim 1, wherein a total reflection layer is on the second side.
 9. The backlight module according to claim 1, wherein the palette device further comprises a second palette LED adjacent to the second side, the second palette LED provides a palette light which passes through the second side into the palette and light-guide bar.
 10. The backlight module according to claim 1, wherein two reflection layers are on the top and the bottom respectively.
 11. The backlight module according to claim 1, wherein the palette and light-guide bar is made of transparent plastic material.
 12. The backlight module according to claim 1, wherein the LED bar is consisted of white LEDs.
 13. The backlight module according to claim 1, wherein the first palette LED is selected from the group of red light LED, green light LED, blue light LED, and multi-color LED.
 14. The backlight module according to claim 10, wherein the second palette LED is selected from the group of red light LED, green light LED, blue light LED, and multi-color LED.
 15. The backlight module according to claim 1, wherein the distance between the first side and the second side is equal to the length of the light-guide plate, the distance between the top and the bottom is equal to the thickness of the light-guide plate.
 16. The backlight module according to claim 1, wherein the first side, the second side, the top, the bottom, and the light-input surface are all slickensides. 